I read on another site that: 1/2 the cylinder measurement + the sphere measurement = diopter strength. Because I have a lot of astigmatism this changes the measurements quite a bit (-3.25 cylinder, -3 sphere). Has anybody else used this equation to...
40139
That's the method we used when buying my daughter's goggles. She ended up with -3.625 (R) and -4.25 (L) so we split the difference with a -4 prescription. She says they work well enough for her, and she has to be read a white board to get her workout during swim practice.
4681
Actually I am not aware of anywhere online that shows measurement. I use the eye dropper bottle that comes with the order and basically do the math myself.I always drink a full glass or cup of distilled water whether I am adding adding 3 drops or 23 drops.
98633
Its actually not bad. I sighted in at 25yds and at 50yds. At 50 it was a little faint but you could definitely see it.. make sure you're not using a bright white paper to sight though as it will wash out. I really wasnt even expecting that for the price. It's worth the 12 bucks.
1238980
The equation for the volume of a sphere is: V=4/3 &#960;r^3 (that weird n should be "pie" as in 3.14159) Thus, the volume of a 60-inch in diameter (30-inch radius) sphere is as follows: V=4/3 &#960;&#12310;(30 in)&#12311;^3((&#12310;2.54 cm)&#12311;^3)/&#12310;(1 inch)&#12311;^3 (1 mL)/&#12310;(1 cm)&#12311;^3 (1 L)/(1000 mL)=1853 Liters But, the volume of the balloon will depend on the pressure required to fill the balloon because the recoil force of the balloon will increase as the diameter increases. Basically, the pressure inside the balloon will be much higher than the surrounding air pressure. And the balloon pressure will increase significantly as the balloon diameter increases and approaches its burst pressure. So, the equation will be: (P1 (at sea level))/(P2 (needed to fill the balloon) )=V2/(V1(at sea level)) I work with angioplasty balloons (those used to treat blood vessel narrowings) daily and the burst pressure in those balloons is between 8 and 25 atmospheres for compliant and non-compliant balloons. This balloon is a compliant balloon (meaning that it changes shape with various pressures), so I would guess that the burst pressure is less than 8 atmospheres - probably more like 4 atmospheres. Thus: Volume =(4 atm)/(1 atm) x 1853 L=7,400 Liters (at atmospheric pressure) But, no fear, you don't have to fill the balloons to full capacity. By filling the balloons to only 40 inches in diameter, the volume and pressure will be substantially less. By my calculations, only 1100 Liters. As far as this information, you know what they say about experts: They know more and more about less and less until they know everything about nothing.
1177291
Depends on what your prescription is. The camera has a built in -3.0 to +1.0 diopter adjustment. You want to buy the one that will allow you to match your prescription.E.g. If you wear +2 prescription, get the +2 and dial it down by 1. You would only need the - if you have to go further than the -3 that is built in. However, I have found that I do not use the diopter. When I have my glasses off, the images on the LCD are blurry. So I shoot with my glasses or contacts, so I can still view the images on the LCD.Hope this helps you decide.Chris
1746
That is the strength of the reading glass. The higher the number the greater the magnification. It is not at all about the size as it will fit your head.
1683132
It depends on what you'd eyeglass prescription is. You should check with you Optomotridt and find out what your prescription is and then get the diopter closest to that.Rich Signorelli
1340325
The first number is the power of the lens, that is how much it will magnify the image. The second number represents the diameter of the lens in mm. They work together to calculate a number called the "exit pupil" or "exit ratio". Take the lens size and divide it by the power to get this number. The higher the number, the brighter the image. For example, 10x50 will give an exit ratio of 5.0, 8x42 would be 5.25, 10x42 would be 4.2. In my opinion, the exit ratio is more important than the power. My favorite binoculars are 8x50 (6.25) but I also just bought 10x50 as a gift who is delighted with that configuration. Stay away from high-power binoculars. They, for me, are too hard to keep steady due to the high magnification. I hope this helps. -Norm
2173896
Not at all. From the description, it is supposed to help people with imperfect vision. I found it pretty useless as I have 20/20. It further seemed like I was looking down a paper towel roll. I am very interested in their other magnifier which can work with a variety of others. Primary Arms makes one but I haven't seen any side by side comparisons.
998685
It says"Magnifier 2 5x ...". I believe the 2 is just part of the product name, there is no decimal point. A 4" lens diameter can't be 5x, they just can't make them. I even asked my eye doctor about ordering one from him. So I think the lens is a 1.5x with a 3x inset as the lower information on the page description says,. I sent mine back as the one I bought at a fabric store was better. I think you could find a 2x or 2.5x in a large lens with a 6x inset somewhere else. The around the neck batteries wear out very fast so you need rechargeable batteries for cost reasons.
1558346
I ordered a pair for myself and 1 pair for each of my sisters in new mexico and texas. We all decided they were not user friendly for us. I don't know the strength but I can tell u this, you cannot see anything unless u hold the item about 1/8th of an inch away from our eyeglasses (we all wear glasses. we were hoping we could get splinters out but we all decided that they would not work for that either. all 3 pairs were thrown in the trash. they just did not work for us. hope this helps u
743771
It's not a graduated cylinder that's for sure. Based on the overall diameter of the location you are taking a measurement I imagine it would be very hard to get consistent readings, just due to parallax. If you're looking for something super accurate, this isn't the right tool.
77652
Yes, somebody here said +.2 or something like that.It is minor but present; makes screen seem just a little bit bigger.You can get them as prescription lenses if you need more.
834168
The first number is the magnification and the second number is the lens diameter. The larger the numbers the more magnification and light gathering potential.
234982
Pardon my terseness, but the answer to this question is clear from the product description. Only two measurements define a cylinder (length and diameter). The product advertises a 3.5" diameter and telescopes to over 36" in length. If your measurements are accurate - then it fits.
1595888
I got 2 lenses with mine (from a year or so ago) a 6mm and a 15mm. The 15mm lens gives a wider field of view while the 6mm lens "zooms" in on the target object for more detail - they should be labeled.The cap with the hole in it is used to calibrate the telescope mirrors (it's called a Collimation cap) - you should not need to use it. If you are interested in all the ins and outs of collimation, you can google it, but I've had my scope for over a year and have not needed to go through the process.
1190631
As per previous answer it is just standard adapter for a camera specific T ring so you can attach camera to telescope that has 1.25 eyepiece It will not give more "strength" (I assume you mean magnification).